[PATCH v3 3/7] ext4: add support FALLOC_FL_COLLAPSE_RANGE for fallocate

[Namjae Jeon]

From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>

Add support FALLOC_FL_COLLAPSE_RANGE for fallocate.

Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Signed-off-by: Ashish Sangwan <a.sangwan@xxxxxxxxxxx>
---
 fs/ext4/ext4.h              |    3 +
 fs/ext4/extents.c           |  286 ++++++++++++++++++++++++++++++++++++++++++-
 fs/ext4/move_extent.c       |    2 +-
 include/trace/events/ext4.h |   25 ++++
 4 files changed, 314 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f3c43fc..a13e0f4 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2737,6 +2737,7 @@ extern int ext4_find_delalloc_cluster(struct inode *inode, ext4_lblk_t lblk);
 extern int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 			__u64 start, __u64 len);
 extern int ext4_ext_precache(struct inode *inode);
+extern int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len);
 
 /* move_extent.c */
 extern void ext4_double_down_write_data_sem(struct inode *first,
@@ -2748,6 +2749,8 @@ void ext4_inode_double_unlock(struct inode *inode1, struct inode *inode2);
 extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
 			     __u64 start_orig, __u64 start_donor,
 			     __u64 len, __u64 *moved_len);
+extern int mext_next_extent(struct inode *inode, struct ext4_ext_path *path,
+			    struct ext4_extent **extent);
 
 /* page-io.c */
 extern int __init ext4_init_pageio(void);
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 54d52af..baf1faf 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4580,12 +4580,16 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	unsigned int credits, blkbits = inode->i_blkbits;
 
 	/* Return error if mode is not supported */
-	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
+	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
+		     FALLOC_FL_COLLAPSE_RANGE))
 		return -EOPNOTSUPP;
 
 	if (mode & FALLOC_FL_PUNCH_HOLE)
 		return ext4_punch_hole(inode, offset, len);
 
+	if (mode & FALLOC_FL_COLLAPSE_RANGE)
+		return ext4_collapse_range(inode, offset, len);
+
 	ret = ext4_convert_inline_data(inode);
 	if (ret)
 		return ret;
@@ -4884,3 +4888,283 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	ext4_es_lru_add(inode);
 	return error;
 }
+
+/*
+ * ext4_access_path:
+ * Function to access the path buffer for marking it dirty.
+ * It also checks if there are sufficient credits left in the journal handle
+ * to update path.
+ */
+static int
+ext4_access_path(handle_t *handle, struct inode *inode,
+		struct ext4_ext_path *path)
+{
+	int credits, err;
+
+	/*
+	 * Check if need to extend journal credits
+	 * 3 for leaf, sb, and inode plus 2 (bmap and group
+	 * descriptor) for each block group; assume two block
+	 * groups
+	 */
+	if (handle->h_buffer_credits < 7) {
+		credits = ext4_writepage_trans_blocks(inode);
+		err = ext4_ext_truncate_extend_restart(handle, inode, credits);
+		/* EAGAIN is success */
+		if (err && err != -EAGAIN)
+			return err;
+	}
+
+	err = ext4_ext_get_access(handle, inode, path);
+	return err;
+}
+
+/*
+ * ext4_ext_shift_path_extents:
+ * Shift the extents of a path structure lying between path[depth].p_ext
+ * and EXT_LAST_EXTENT(path[depth].p_hdr) downwards, by subtracting shift
+ * from starting block for each extent.
+ */
+static int
+ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
+			    struct inode *inode, handle_t *handle,
+			    ext4_lblk_t *start)
+{
+	int depth, err = 0;
+	struct ext4_extent *ex_start, *ex_last;
+	bool update = 0;
+	depth = path->p_depth;
+
+	while (depth >= 0) {
+		if (depth == path->p_depth) {
+			ex_start = path[depth].p_ext;
+			if (!ex_start)
+				return -EIO;
+
+			ex_last = EXT_LAST_EXTENT(path[depth].p_hdr);
+			if (!ex_last)
+				return -EIO;
+
+			err = ext4_access_path(handle, inode, path + depth);
+			if (err)
+				goto out;
+
+			if (ex_start == EXT_FIRST_EXTENT(path[depth].p_hdr))
+				update = 1;
+
+			*start = ex_last->ee_block +
+				ext4_ext_get_actual_len(ex_last);
+
+			while (ex_start <= ex_last) {
+				ex_start->ee_block -= shift;
+				ext4_ext_try_to_merge(handle, inode,
+						path, ex_start);
+				ex_start++;
+			}
+			err = ext4_ext_dirty(handle, inode, path + depth);
+			if (err)
+				goto out;
+
+			if (--depth < 0 || !update)
+				break;
+		}
+
+		/* Update index too */
+		err = ext4_access_path(handle, inode, path + depth);
+		if (err)
+			goto out;
+
+		path[depth].p_idx->ei_block -= shift;
+		err = ext4_ext_dirty(handle, inode, path + depth);
+		if (err)
+			goto out;
+
+		/* we are done if current index is not a starting index */
+		if (path[depth].p_idx != EXT_FIRST_INDEX(path[depth].p_hdr))
+			break;
+
+		depth--;
+	}
+
+out:
+	return err;
+}
+
+/*
+ * ext4_ext_shift_extents:
+ * All the extents which lies in the range from start to the last allocated
+ * block for the file are shifted downwards by shift blocks.
+ * On success, 0 is returned, error otherwise.
+ */
+static int
+ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
+		       ext4_lblk_t start, ext4_lblk_t shift)
+{
+	struct ext4_ext_path *path;
+	int ret = 0, depth;
+	struct ext4_extent *extent;
+	ext4_lblk_t stop_block, current_block;
+	ext4_lblk_t ex_start, ex_end;
+
+	/* Let path point to the last extent */
+	path = ext4_ext_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
+	depth = path->p_depth;
+	extent = path[depth].p_ext;
+	if (!extent) {
+		ext4_ext_drop_refs(path);
+		kfree(path);
+		return ret;
+	}
+
+	stop_block = extent->ee_block + ext4_ext_get_actual_len(extent);
+	ext4_ext_drop_refs(path);
+	kfree(path);
+
+	/* Nothing to shift, if hole is at the end of file */
+	if (start >= stop_block)
+		return ret;
+
+	/*
+	 * Don't start shifting extents until we make sure the hole is big
+	 * enough to accomodate the shift.
+	 */
+	path = ext4_ext_find_extent(inode, start - 1, NULL, 0);
+	depth = path->p_depth;
+	extent =  path[depth].p_ext;
+	ex_start = extent->ee_block;
+	ex_end = extent->ee_block + ext4_ext_get_actual_len(extent);
+	ext4_ext_drop_refs(path);
+	kfree(path);
+
+	if ((ex_start > start - 1 && shift > ex_start) ||
+	    (ex_end > start - shift))
+		return -EIO;
+
+	/* Its safe to start updating extents */
+	while (start < stop_block) {
+		path = ext4_ext_find_extent(inode, start, NULL, 0);
+		if (IS_ERR(path))
+			return PTR_ERR(path);
+		depth = path->p_depth;
+		extent = path[depth].p_ext;
+		current_block = extent->ee_block;
+		if (start > current_block) {
+			/* Hole, move to the next extent */
+			ret = mext_next_extent(inode, path, &extent);
+			if (ret != 0) {
+				ext4_ext_drop_refs(path);
+				kfree(path);
+				if (ret == 1)
+					ret = 0;
+				break;
+			}
+		}
+		ret = ext4_ext_shift_path_extents(path, shift, inode,
+				handle, &start);
+		ext4_ext_drop_refs(path);
+		kfree(path);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/*
+ * ext4_collapse_range:
+ * This implements the fallocate's collapse range functionality for ext4
+ * Returns: 0 and non-zero on error.
+ */
+int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
+{
+	struct super_block *sb = inode->i_sb;
+	ext4_lblk_t punch_start, punch_stop;
+	handle_t *handle;
+	unsigned int credits;
+	unsigned int rounding;
+	loff_t ioffset, new_size;
+	int ret;
+
+	if (!S_ISREG(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	if (EXT4_SB(sb)->s_cluster_ratio > 1)
+		return -EOPNOTSUPP;
+
+	/* Currently just for extent based files */
+	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
+		return -EOPNOTSUPP;
+
+	if (IS_SWAPFILE(inode))
+		return -ETXTBSY;
+
+	trace_ext4_collapse_range(inode, offset, len);
+
+	punch_start = offset >> EXT4_BLOCK_SIZE_BITS(sb);
+	punch_stop = (offset + len) >> EXT4_BLOCK_SIZE_BITS(sb);
+
+	rounding = max_t(uint, 1 << EXT4_BLOCK_SIZE_BITS(sb), PAGE_CACHE_SIZE);
+	ioffset = offset & ~(rounding - 1);
+
+	/* Write out all dirty pages */
+	ret = filemap_write_and_wait_range(inode->i_mapping, ioffset, -1);
+	if (ret)
+		return ret;
+
+	/* Take mutex lock */
+	mutex_lock(&inode->i_mutex);
+
+	/* Wait for existing dio to complete */
+	ext4_inode_block_unlocked_dio(inode);
+	inode_dio_wait(inode);
+
+	truncate_pagecache_range(inode, ioffset, -1);
+
+	credits = ext4_writepage_trans_blocks(inode);
+	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
+	if (IS_ERR(handle)) {
+		ret = PTR_ERR(handle);
+		goto out_dio;
+	}
+
+	down_write(&EXT4_I(inode)->i_data_sem);
+
+	ext4_discard_preallocations(inode);
+
+	ret = ext4_es_remove_extent(inode, punch_start,
+				    EXT_MAX_BLOCKS - punch_start - 1);
+	if (ret)
+		goto journal_stop;
+
+	ret = ext4_ext_remove_space(inode, punch_start, punch_stop - 1);
+	if (ret)
+		goto journal_stop;
+
+	ret = ext4_ext_shift_extents(inode, handle, punch_stop,
+				     punch_stop - punch_start);
+	if (ret)
+		goto journal_stop;
+
+	if ((offset + len) > i_size_read(inode))
+		new_size = offset;
+	else
+		new_size = i_size_read(inode) - len;
+
+	truncate_setsize(inode, new_size);
+	EXT4_I(inode)->i_disksize = new_size;
+
+	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
+	ext4_mark_inode_dirty(handle, inode);
+
+journal_stop:
+	ext4_journal_stop(handle);
+	up_write(&EXT4_I(inode)->i_data_sem);
+
+out_dio:
+	ext4_inode_resume_unlocked_dio(inode);
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 7fa4d85..4cbebb0 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -76,7 +76,7 @@ copy_extent_status(struct ext4_extent *src, struct ext4_extent *dest)
  * ext4_ext_path structure refers to the last extent, or a negative error
  * value on failure.
  */
-static int
+int
 mext_next_extent(struct inode *inode, struct ext4_ext_path *path,
 		      struct ext4_extent **extent)
 {
diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index 197d312..90e2f71 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -2410,6 +2410,31 @@ TRACE_EVENT(ext4_es_shrink_exit,
 		  __entry->shrunk_nr, __entry->cache_cnt)
 );
 
+TRACE_EVENT(ext4_collapse_range,
+	TP_PROTO(struct inode *inode, loff_t offset, loff_t len),
+
+	TP_ARGS(inode, offset, len),
+
+	TP_STRUCT__entry(
+		__field(dev_t,	dev)
+		__field(ino_t,	ino)
+		__field(loff_t,	offset)
+		__field(loff_t, len)
+	),
+
+	TP_fast_assign(
+		__entry->dev	= inode->i_sb->s_dev;
+		__entry->ino	= inode->i_ino;
+		__entry->offset	= offset;
+		__entry->len	= len;
+	),
+
+	TP_printk("dev %d,%d ino %lu offset %lld len %lld",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned long) __entry->ino,
+		  __entry->offset, __entry->len)
+);
+
 #endif /* _TRACE_EXT4_H */
 
 /* This part must be outside protection */
-- 
1.7.9.5

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